Method and apparatus for evaluation of coated parts

Abstract

A method of verifying performance of a coated part includes calculating a deflection value as a function of a predetermined strain threshold value and a total thickness of a test coupon that comprises a coating on a substrate. The coating of the test coupon is co-deposited in a deposition process for producing a coated part. The test coupon is bent in an amount equal to the calculated deflection value and then evaluated as an indication of whether a mechanical characteristic of the coated part meets a specified level.

1. A method of verifying performance of a coated part, comprising:
 calculating a deflection value (δ) as a function of a predetermined strain threshold value (ε) and a total thickness (t) of a test coupon comprising a coating on a substrate, wherein the coating of the test coupon was co-deposited in a deposition process for producing a coated part; 
 deflecting the test coupon in amount equal to the deflection value (δ); and 
 evaluating the coating of the test coupon after the deflecting as an indication of whether a mechanical characteristic of the coated part meets a specified level. 
 
     
     
       2. The method as recited in  claim 1 , wherein δ=ε(k 1 −k 2 t) and k 1  and k 2  are geometry-based constants. 
     
     
       3. The method as recited in  claim 1 , wherein the deflecting is conducted in a four-point bending fixture. 
     
     
       4. The method as recited in  claim 1 , wherein the evaluating of the coating includes determining whether the coating has cracked. 
     
     
       5. The method as recited in  claim 1 , wherein the mechanical characteristic is fatigue performance of the coated part. 
     
     
       6. The method as recited in  claim 1 , wherein the coating comprises cobalt and phosphorous. 
     
     
       7. A method of verifying performance of a coated part, comprising:
 co-depositing a coating onto a substrate of a test coupon and a part to produce a test coupon comprising the coating on a substrate and a coated part; 
 calculating a deflection value (δ) as a function of a predetermined strain threshold value (ε) and a total thickness (t) of the test coupon; 
 deflecting the test coupon in amount equal to the deflection value (δ); and 
 evaluating whether coating of the test coupon has cracked after the deflecting as an indication of whether a fatigue performance of the coated part meets a specified level. 
 
     
     
       8. The method as recited in  claim 7 , wherein the co-depositing includes electrodeposition. 
     
     
       9. The method as recited in  claim 7 , wherein the coating comprises cobalt and phosphorous. 
     
     
       10. The method as recited in  claim 1 , wherein the predetermined strain threshold value (ε) is directly proportional to a mechanical characteristic of the coated part. 
     
     
       11. The method as recited in  claim 1 , wherein the predetermined strain threshold value (ε) is a strain below which the coated part meets a predetermined level of fatigue performance. 
     
     
       12. The method as recited in  claim 1 , wherein in the deflecting of the test coupon, there is a first possible outcome where the coating of the test coupon cracks and a second possible outcome where the coating of the test coupon does not crack, and the evaluating of the coating of the test coupon is based upon which one of the first possible outcome or the second possible outcome occurs. 
     
     
       13. A method of verifying performance of a coated part, comprising:
 providing a test coupon including a coating on a substrate, wherein the coating on the test coupon was deposited in unison with deposition of the coating onto a part to provide a coated part; 
 calculating a deflection value (δ) as a function of a predetermined strain threshold value (ε) of the coated part and a total thickness (t) of the test coupon, the predetermined strain threshold value (ε) corresponding to a predetermined level of fatigue performance of the coated part; 
 deflecting the test coupon in amount equal to the deflection value (δ); and 
 determining whether the coating of the test coupon cracked under the deflecting such that the presence of cracking of the coating of the test coupon signifies that the coated part does not meet the specified level of fatigue performance.